我的android studio没什么问题。我正在尝试从URL下载图像,然后使用AsyncTask在Imageview中显示它。但是,当我单击按钮时,您看到的只是进度对话框,然后imageview变为空白。
我确实在清单文件中插入了INTERNET权限。
提前致谢
package com.phil.imagesdemo;
import androidx.appcompat.app.AppCompatActivity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import java.io.InputStream;
public class MainActivity extends AppCompatActivity {
String url = "https://en.wikipedia.org/wiki/Bart_Simpson#/media/File:Bart_Simpson_200px.png";
ImageView image;
Button button;
ProgressDialog mProgressDialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
image = (ImageView) findViewById(R.id.theImage);
button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new DownloadImage().execute(url);
}
});
}
private class DownloadImage extends AsyncTask{
@Override
protected Bitmap doInBackground(Object... urls) {
String imageURL = (String)urls[0];
Bitmap bitmap = null;
try {
// Download Image from URL
InputStream input = new java.net.URL(imageURL).openStream();
// Decode Bitmap
bitmap = BitmapFactory.decodeStream(input);
} catch (Exception e) {
e.printStackTrace();
}
return bitmap;
}
@Override
protected void onPostExecute(Object result) {
super.onPostExecute(result);
// Set the bitmap into ImageView
image.setImageBitmap ((Bitmap)result);
// Close progressdialog
mProgressDialog.dismiss();
}
@Override
protected void onPreExecute() {
super.onPreExecute();
mProgressDialog = new ProgressDialog(MainActivity.this);
mProgressDialog.setTitle("Download Image Tutorial");
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
mProgressDialog.show();
}
}
}
清单文件
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.phil.imagesdemo">
<uses-permission android:name="android.permission.INTERNET" ></uses-permission>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
最佳答案
好了,经过长时间的努力,我发现错误消息是套接字失败:EPERM(不允许操作)。
我只需要从模拟器中卸载应用程序,然后再次运行即可